Field of the Invention
The invention relates to a device for measuring the rotation speed or detecting the direction of rotation of a rotary magnetic field.
A device that is known from European Patent 0 363 738 B1 has a holder that holds the Hall sensor in such a way that a magnetic field can readily be detected. The Hall sensor is connected to an evaluation circuit on a printed circuit board through electrical contacts that are passed through the holder. However, such a holder is very complicated and expensive to produce. Moreover, the Hall sensor requires complicated adjustment.
Another device for measuring the rotation speed or detecting the direction of rotation of a rotary magnetic field, which is known from U.S. Pat. No. 4,110,676, has a rotating rotor spindle on which a magnet wheel is secured. The north and south poles of the magnet wheel are disposed in such a way that the direction of magnetization and therefore the magnetic field are oriented radially. In addition, a magnetic flux guide element which is provided parallel to the field lines focuses the magnetic field lines onto a Hall sensor. In that device, the Hall sensor must be disposed perpendicular to the field lines and to the magnetic flux guide element. The magnetic field lines are not deflected by the magnetic flux guide element.
In an electric motor with a rotary field measurement between a rotor-side magnet field with magnet poles in a plane perpendicular to a rotor axis and a Hall element on a printed circuit board, which is known from U.S. Pat. No. 4,857,784, a sensor surface is disposed perpendicular to a printed circuit board and closely parallel to a circumferential surface of a magnet wheel. The printed circuit board lies radially inside a fixing edge of a bearing receptacle, which for its part is introduced in an assembled motor in a rotating matched receptacle edge of a motor housing of the electric motor.
German Utility Model DE 91 06 064 U1 discloses a device in which a permanent magnet that has a plurality of north and south poles is secured to a rotor axis. Two disk-like magnetic flux guide elements are disposed between the north and south poles, each having one north pole and one south pole, so that a magnetic field is generated between them. A Hall sensor that measures the direction of magnetization is disposed in the magnetic field. In that device, the magnetic flux guide elements are used to form poles of the magnets.